Dynamic haptic retargeting5

ABSTRACT

Dynamic haptic retargeting can be implemented using world warping techniques and body warping techniques. World warping is applied to improve an alignment between a virtual object and a physical object, while body warping is applied to redirect a user&#39;s motion to increase a likelihood that a physical hand will reach the physical object at the same time a virtual representation of the hand reaches the virtual object. Threshold values and/or a combination of world warping a body warping can be used to mitigate negative impacts that may be caused by using either technique excessively or independently.

BACKGROUND

Virtual reality systems are becoming ever more popular, withconsumer-level head-mounted displays and motion tracking devices leadingto the creation of a large number of immersive experiences. A primaryobjective in many virtual reality systems is to establish a sense ofpresence for the user. While optics, rendering, and audio technologieshave improved substantially, resulting in photorealistic renderingsthrough which users can be convinced by the illusion of reality, a senseof touch expected when reaching out and grabbing virtual objects isstill lacking.

Haptics is a term used to represent various aspects of a user's sense oftouch. One method for enabling users to experience a sense of touch wheninteracting with virtual objects is referred to herein as passivehaptics. Mapping respective physical objects to each virtual object withwhich a user is expected to interact can result in a compelling tactilesensation when reaching out and touching a virtual object. However, thisillusion requires each virtual object to have a corresponding physicalprop of the same size and shape and in the same location. This canresult in a very complicated physical environment, and keeping thephysical environment synchronized with the virtual environment can bedifficult or even impossible.

SUMMARY

This disclosure describes techniques for dynamic haptic retargeting. Asingle physical object can be mapped to multiple virtual objects suchthat when a user reaches out to touch any one of the virtual objects,the dynamic haptic retargeting techniques result in redirection of theuser's physical movement so that, when it appears to the user that theyare touching the virtual object, they are actually touching the physicalobject. A variety of techniques can be used to implement dynamic hapticretargeting, including, but not limited to, world warping, body warping,and a combination of world and body warping.

According to an example world warping technique, the virtual environmentis shifted with regard to the physical environment, for example, bytranslation or rotation. According to an example body warping technique,the virtual representation of a user's hand is manipulated to passivelyredirect the user's physical motions while reaching for a virtualobject.

In at least some scenarios, by applying a combination of world warpingand body warping and/or by enforcing a maximum warp for either or both,negative effects such as detectable world warping, motion sickness,and/or virtual body misalignment may be reduced.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key or essentialfeatures of the claimed subject matter, nor is it intended to be used asan aid in determining the scope of the claimed subject matter. The term“techniques,” for instance, may refer to system(s), method(s),computer-readable instructions, module(s), algorithms, hardware logic,and/or operation(s) as permitted by the context described above andthroughout the document.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Thesame reference numbers in different figures indicate similar oridentical items.

FIG. 1 is a pictorial diagram illustrating an example environment inwhich dynamic haptic retargeting can be implemented.

FIG. 2 is a pictorial diagram illustrating an example mapping of avirtual environment to a physical environment.

FIG. 3 is a pictorial diagram illustrating an example of world warping.

FIG. 4 is a pictorial diagram illustrating an example of body warping.

FIG. 5 is a pictorial diagram illustrating an example of a combinationof world warping and body warping.

FIG. 6 is a block diagram illustrating select components of a hapticretargeting system.

FIG. 7 is a flow diagram of an example method for performing dynamichaptic retargeting.

FIG. 8 is a flow diagram of an example method for applying a world warpto perform dynamic haptic retargeting.

FIG. 9 is a flow diagram of an example method for determining a maximumworld warp based on a change in a user's head position.

FIG. 10 is a flow diagram of an example method for applying a body warpto perform dynamic haptic retargeting.

FIG. 11 is a pictorial diagram illustrating an example incremental bodywarp.

FIG. 12 is a flow diagram of an example method for applying anincremental body warp.

FIG. 13 is a flow diagram of an example method for applying abody-friendly body warp.

DETAILED DESCRIPTION Overview

Techniques for dynamic haptic retargeting are described herein. When auser is interacting with a virtual reality or mixed reality environment,repurposing a single physical object to provide passive haptic sensationfor a variety of virtual objects, can increase the user's sense ofpresence within the environment and can increase the overall quality ofthe experience. As an example, a user may be interacting with a virtualreality environment that includes multiple similar objects. As definedwithin the virtual reality environment, the virtual objects can bepicked up and their positions manipulated by the user. Using the dynamichaptic retargeting techniques described herein, a single physical objecthaving similar size and shape to the virtual objects represented in thevirtual reality can be used to provide passive haptic feedback to theuser when the user touches any of the virtual objects.

Dynamic haptic retargeting enables a single physical object to be mappedto multiple virtual objects by altering the user's perception of theuser's physical position with respect to the virtual environment. Forexample, if there are two virtual objects and both are mapped to asingle physical object, as the user reaches for either of the virtualobjects, the user's physical movements are dynamically redirected towardthe single physical object, while visually the user sees a virtualrepresentation of the user's hand reaching toward the virtual object theuser has chosen.

Dynamic haptic retargeting techniques, as described herein, includeworld warping, body warping, and a combination of the two. According toa world warping technique, as a user reaches for a virtual object, thevirtual environment with which the user is interacting is rotated toalign a position of the virtual object with a position of the physicalobject. According to a body warping technique, as a user reaches for avirtual object, a position of a virtual representation of the user'shand and arm within the virtual environment is altered, causing the userto adjust the direction of their movement so that the user's handreaches the physical object as the virtual representation of the user'shand reaches the virtual object.

Both world warping and body warping techniques have drawbacks. Forexample, if applied excessively, world warping can cause the user tofeel motion sickness. Furthermore, even smaller amounts of world warping(e.g., not significant enough to cause motion sickness) may be visiblydetected by a user, which may result in the user becoming aware that thephysical object is not the same as the virtual object. As anotherexample, if applied excessively, body warping can result in a virtualrepresentation of the user's arm or hand that appears out of alignmentwith the rest of the user's body or the virtual representation of theuser's arm may appear unnaturally deformed.

Effective haptic retargeting can be achieved by dynamically applyingworld warping, body warping, or a combination of world warping and bodywarping as a user interacts with a virtual environment.

Illustrative Environment

FIG. 1 illustrates an example environment 100 in which dynamic hapticretargeting can be implemented. In the illustrated example, a user 102is in a physical environment, which includes a table 104 and a physicalobject 106. A virtual environment is mapped to the physical environment,and includes virtual object 108 and virtual object 110.

Example environment 100 also include any number of a devices to enablethe user 102 to interact with the virtual environment. For example,example environment 100 includes device 112, implemented as ahead-mounted display, camera 114, and hand tracking device 116.

Device 112 is illustrated as a head-mounted display, but isrepresentative of any device that enables a user to interact withvirtual objects in a virtual environment. In the illustrated example,device 112 includes a processor 118, one or more sensors 120, inputinterface 122, and memory 124, each operably connected to the otherssuch as via a bus 125. Bus 125 may include, for example, one or more ofa system bus, a data bus, an address bus, a PCI bus, a Mini-PCI bus, andany variety of local, peripheral, and/or independent buses.

Processor 118 can represent, for example, a CPU-type processing unit, aGPU-type processing unit, a field-programmable gate array (FPGA),another class of digital signal processor (DSP), or other hardware logiccomponents that may, in some instances, be driven by a CPU. For example,and without limitation, illustrative types of hardware logic componentsthat can be used include Application-Specific Integrated Circuits(ASICs), Application-Specific Standard Products (ASSPs),System-on-a-chip systems (SOCs), Complex Programmable Logic Devices(CPLDs), etc.

Sensors 120 may include, for example, a depth map sensor, a camera, alight field sensor, a gyroscope, a sonar sensor, an infrared sensor, acompass, an accelerometer, and/or any other component for detecting aposition or movement of the device 112 and/or other objects. Sensors 120can also enable the generation of data characterizing interactions, suchas user gestures, with the device 112.

I/O (input/output) interface 122 is configured to enable device 112 toreceive input or send output. For example, input may be received via atouch screen, a camera to receive gestures, a microphone, a keyboard, amouse, or any other type of input device. Similarly, for example, outputmay be presented via a display, speakers, or any other output device.

Memory 124 can store instructions executable by the processor 118. Forexample, memory 124 can store a virtual reality system 126 that can beexecuted to enable user interaction with virtual objects within avirtual environment. Furthermore memory 124 can store a hapticretargeting system 128 that can be executed to support user interactionwith the virtual environment through the use of dynamic hapticretargeting.

Camera 114 may be implemented to capture motions of the user. Datagenerated by camera 114 may then be used, for example, to generate avirtual representation of a user's hand within the virtual environment.In an example implementation, data from camera 114 is communicated tohaptic retargeting system 128 via, for example, a network 130.

Example environment 100 may also include a server computer system 132.Example server 132 includes a processor 134 and a memory 136, operablyconnected to each other such as via a bus 137. Bus 137 may include, forexample, one or more of a system bus, a data bus, an address bus, a PCIbus, a Mini-PCI bus, and any variety of local, peripheral, and/orindependent buses. An operating system 138 and all or part of virtualreality system 126 and/or haptic retargeting system 128 may be stored inmemory 136 and executed on processor 134.

Memory 124 and memory 136 are examples of computer-readable media. Asdescribed above, memory 124 and memory 136 can store instructionsexecutable by processors 118 and 134. Computer-readable media (e.g.,memory 124 and/or memory 136) can also store instructions executable byexternal processing units such as by an external CPU, an external GPU,and/or executable by an external accelerator, such as an FPGA typeaccelerator, a DSP type accelerator, or any other internal or externalaccelerator. In various examples at least one CPU, GPU, and/oraccelerator is incorporated in device 112, while in some examples one ormore of a CPU, GPU, and/or accelerator is external to device 112.

Computer-readable media may include computer storage media and/orcommunication media. Computer storage media can include volatile memory,nonvolatile memory, and/or other persistent and/or auxiliary computerstorage media, removable and non-removable computer storage mediaimplemented in any method or technology for storage of information suchas computer-readable instructions, data structures, program modules, orother data. Memory 124 and memory 136 can be examples of computerstorage media. Thus, the memory 124 and memory 136 includes tangibleand/or physical forms of media included in a device and/or hardwarecomponent that is part of a device or external to a device, includingbut not limited to random-access memory (RAM), static random-accessmemory (SRAM), dynamic random-access memory (DRAM), phase change memory(PRAM), read-only memory (ROM), erasable programmable read-only memory(EPROM), electrically erasable programmable read-only memory (EEPROM),flash memory, compact disc read-only memory (CD-ROM), digital versatiledisks (DVDs), optical cards or other optical storage media, magneticcassettes, magnetic tape, magnetic disk storage, magnetic cards or othermagnetic storage devices or media, solid-state memory devices, storagearrays, network attached storage, storage area networks, hosted computerstorage or any other storage memory, storage device, and/or storagemedium that can be used to store and maintain information for access bya computing device.

In contrast to computer storage media, communication media may embodycomputer-readable instructions, data structures, program modules, orother data in a modulated data signal, such as a carrier wave, or othertransmission mechanism. As defined herein, computer storage media doesnot include communication media. That is, computer storage media doesnot include communications media consisting solely of a modulated datasignal, a carrier wave, or a propagated signal, per se.

Device 112 and/or server 130 can belong to a variety of categories orclasses of devices such as traditional server-type devices, desktopcomputer-type devices, mobile-type devices, special purpose-typedevices, embedded-type devices, and/or wearable-type devices. Thus,although illustrated as a single type of device, device 112 and server130 can include a diverse variety of device types and are not limited toa particular type of device. Device 112 and server 130 can represent,but are not limited to, desktop computers, server computers, web-servercomputers, personal computers, mobile computers, laptop computers,tablet computers, wearable computers, implanted computing devices,telecommunication devices, thin clients, terminals, personal dataassistants (PDAs), game consoles, gaming devices, work stations, mediaplayers, personal video recorders (PVRs), set-top boxes, cameras,integrated components for inclusion in a computing device, appliances,or any other sort of computing device.

Network 128 can include, for example, public networks such as theInternet, private networks such as an institutional and/or personalintranet, or some combination of private and public networks. Network128 can also include any type of wired and/or wireless network,including but not limited to local area networks (LANs), wide areanetworks (WANs), satellite networks, cable networks, Wi-Fi networks,WiMax networks, mobile communications networks (e.g., 3G, 4G, and soforth) or any combination thereof. Network 128 can utilizecommunications protocols, including packet-based and/or datagram-basedprotocols such as internet protocol (IP), transmission control protocol(TCP), user datagram protocol (UDP), or other types of protocols.Moreover, network 128 can also include a number of devices thatfacilitate network communications and/or form a hardware basis for thenetworks, such as switches, routers, gateways, access points, firewalls,base stations, repeaters, backbone devices, and the like.

In some examples, network 128 can further include devices that enableconnection to a wireless network, such as a wireless access point (WAP).Examples support connectivity through WAPs that send and receive dataover various electromagnetic frequencies (e.g., radio frequencies),including WAPs that support Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 standards (e.g., 802.11g, 802.11n, and soforth), and other standards.

FIG. 2 illustrates an example mapping of a virtual environment 202 to aphysical environment 204. As discussed above with reference to FIG. 1,physical environment 204 includes a table 104 and a physical object 106,illustrated as a block or cube. Similarly, virtual environment 202includes a virtual table 206, virtual object 108, and virtual object110. View 208 illustrates the virtual environment 202 mapped onto thephysical environment 204 such that table 104 and virtual table 206 arealigned, and each of physical object 106 and virtual objects 108 and 110appear to be resting on the table.

Although not illustrated, device 112, camera 114, and server 132 mayeach also include a network interface to facilitate communication vianetwork 130.

World Warping and Body Warping

FIG. 3 illustrates an example of dynamic world warping as a user reachestoward a virtual object. View 302 corresponds to view 208 of FIG. 2,which illustrates a virtual environment mapped onto a physicalenvironment. Furthermore, view 302 includes a virtual representation ofa user's hand 304, as the user reaches toward virtual object 108.Because physical object 106 and virtual object 108 are not aligned withone another, if the reaches for virtual object 108, the user will notphysically come in contact with physical object 106. World warping is atechnique that can be used to enable dynamic haptic retargeting byrealigning the virtual environment 202 with the physical environment 204so that the virtual object 108 being reached for is aligned with thephysical object 106. View 306 illustrates a result of applying a worldwarping to move the virtual environment 202 with respect to the physicalenvironment 204 to align virtual object 108 with physical object 106.

FIG. 4 illustrates an example of dynamic body warping as a user reachestoward a virtual object. View 402 corresponds to view 208 of FIG. 2,which illustrates a virtual environment mapped onto a physicalenvironment. Furthermore, view 402 includes a virtual representation ofa user's hand 404, as the user reaches toward virtual object 108. As inthe scenario described above with reference to FIG. 3, because physicalobject 106 and virtual object 108 are not aligned with one another, ifthe user reaches for virtual object 108, the user will not physicallycome in contact with physical object 106. Body warping is anothertechnique that can be used to enable dynamic haptic retargeting byaltering the location of the virtual representation of the user's hand404 to cause the user to change their physical motion such that theuser's physical hand will come in contact with physical object 106 whenthe virtual representation of the user's hand 404 comes in contact withthe virtual object 108.

View 406 illustrates an example body warping in which the virtualrepresentation of the user's hand 404 is moved to the left 408 to a newlocation 404′. Based on this adjustment, the user will physically movetheir hand further to the right, thereby physically reaching for thephysical object 106 while it appears the virtual representation of theuser's hand 404′ is reaching for the virtual object 108.

FIG. 5 illustrates an example of dynamic haptic retargeting using acombination of world warping and body warping. View 502 corresponds toview 208 of FIG. 2, which illustrates a virtual environment mapped ontoa physical environment. Furthermore, view 502 includes a virtualrepresentation of a user's hand 504, as the user reaches toward virtualobject 108. As in the scenarios described above with reference to FIGS.2 and 3, because physical object 106 and virtual object 108 are notaligned with one another, if the reaches for virtual object 108, theuser will not physically come in contact with physical object 106. View506 illustrates a result of a dynamic world warping which results invirtual object 108 being closer to physical object 106. View 508illustrates a result of a dynamic body warping applied after the dynamicworld warping shown in view 506. By applying a combination of worldwarping and body warping, each can be applied to a lesser degree than ifonly one is applied.

Example Haptic Retargeting System

FIG. 6 illustrates select components of an example haptic retargetingsystem 128, which includes virtual target detection module 602, physicaltarget selection module 604, and warp control module 606. As describedabove with reference to FIG. 1, one or more individual components, orportions of individual components, of the haptic retargeting system 128can be implemented as part of device 112 and/or server 132, or any otherdevice communicatively connected to device 112.

Target detection module 602 determines a virtual object toward which auser is reaching. Any number of techniques may be used to detect thetarget virtual object. For example, a user may indicate the target via auser interface selection or via a voice command. As another example,device 112 may include sensors to facilitate gaze detection, and atarget virtual object may be detected based on a determined gazedirection. As another example, a vector may be generated based on auser's reach, and a virtual object nearest an intersection with thevector may be detected as the target virtual object.

Physical target selection module 604 selects a physical object to bemapped to the detected target virtual object. Any number of techniquesmay be used to select the target physical object. As an example, ifmultiple physical objects are in the physical environment, the physicalobject closest to the target virtual object may be selected. As anotherexample, if multiple physical objects are in the physical environment, aphysical object that most closely resembles the target virtual objectmat by selected. In another example, the closest physical object thatresembles the target virtual object may be selected as the targetphysical object. In yet another example, any of the above criteria maybe used in conjunction with determining a physical object for which apath between the user's physical hand and the physical object does notintersect any other physical or virtual objects.

Warp control module 606 controls the application of world warp and/orbody warp to facilitate dynamic haptic retargeting. Warp control module606 includes world warp module 608 and body warp module 610. World warpmodule 608 dynamically applies world warping to incrementally alter thealignment of the virtual environment with the physical environment as auser reaches toward a virtual object. Body warp module 610 dynamicallyapplies body warping to incrementally modify the location of the virtualrepresentation of the user's hand as the user reaches toward the virtualobject.

Methods for Dynamic Haptic Retargeting

FIGS. 7-12 illustrate example methods for performing dynamic hapticretargeting. The example processes are illustrated as collections ofblocks in logical flow graphs, which represent sequences of operationsthat can be implemented in hardware, software, or a combination thereof.The blocks are referenced by numbers. In the context of software, theblocks represent computer-executable instructions stored on one or morecomputer-readable media that, when executed by one or more processingunits (such as hardware microprocessors), perform the recitedoperations. Generally, computer-executable instructions includeroutines, programs, objects, components, data structures, and the likethat perform particular functions or implement particular abstract datatypes. The order in which the operations are described is not intendedto be construed as a limitation, and any number of the described blockscan be combined in any order and/or in parallel to implement theprocess.

FIG. 7 illustrates an example method 700 for performing dynamic hapticretargeting. At block 702, a virtual environment is aligned with aphysical environment. For example, as described above with reference toFIGS. 1 and 2, virtual reality system 125 aligns virtual environment 202with physical environment 204.

At block 704, a target virtual object is detected within the virtualenvironment. For example, virtual target detection module 602 detects avirtual object that is a target of a user's reach. For example, asdescribed above with reference to FIG. 6, virtual target detectionmodule may use any number of techniques to detect the target virtualobject, including, but not limited to, user selection through a userinterface or voice command, gaze detection, or analysis of motion of theuser's hand.

At block 706, a virtual location of the target virtual object isdetermined. For example, virtual reality system 125 tracks the locationof each virtual object.

At block 708, a target physical object is selected within the physicalenvironment. For example, physical target selection module 604 selects aphysical object to be mapped to the target virtual object. For example,as described above with reference to FIG. 6, any number of techniquesmay be used to select the target physical object. For example, ifmultiple physical objects are candidates, a physical object closest tothe target virtual object may be selected, a physical object that mostclosely resembles the target virtual object may be selected, or aphysical object having a texture represented by the target virtualobject may be selected.

At block 710, a physical location of the target physical object isdetermined. For example, virtual reality system 126 may be configured tomaintain location data associated with each physical object in thephysical environment to which the virtual environment is mapped.

At block 712, it is determined whether or not the virtual location ofthe target virtual object is aligned with the physical location of thetarget physical object. For example, warp control module 606 compares alocation of the target virtual object with a location of the targetphysical object. If the locations are within a threshold distance of oneanother, then it is determined that the target virtual object and thetarget physical object are aligned.

If the virtual location of the target virtual object is aligned with thephysical location of the target physical object (the “Yes” branch fromblock 712), then at block 714, the method ends as there is no need toperform a world warp or a body warp.

On the other hand, if the virtual location of the target virtual objectis not aligned with the physical location of the target physical object(the “No” branch from block 712), then at block 716, a world warp isdynamically applied as the user reaches toward the virtual object.

At block 718, warp control module 606 determines whether or not thevirtual location of the target virtual object is aligned with thephysical location of the target physical object. For example, warpcontrol module 606 compares a location of the target virtual object(after the world warp has been applied) with a location of the targetphysical object. If the locations are within a threshold distance of oneanother, then it is determined that the target virtual object and thetarget physical object are aligned.

If the virtual location of the target virtual object is aligned with thephysical location of the target physical object (the “Yes” branch fromblock 718), then at block 714, the method ends as there is no need toperform a body warp or an additional world warp.

On the other hand, if the virtual location of the target virtual objectis not aligned with the physical location of the target physical object(the “No” branch from block 718), then at block 720, a body warp isdynamically applied as the user reaches toward the virtual object.

Processing continues as described above with reference to block 712. Inan example implementation, blocks 712-720 are performed repeatedly as auser reaches toward the target virtual object. These steps may beperformed periodically based on a pre-defined time interval. Forexample, the steps represented by blocks 712-720 may be performed foreach frame of data captured by a sensor 120.

FIG. 8 illustrates an example method 716 for dynamically applying aworld warp as the user reaches toward a virtual object. At block 802, alocation difference between the physical location of the target physicalobject and the virtual location of the target virtual object iscalculated. For example, virtual reality system 126 maintains locationdata for the target virtual object and the target physical object. In anexample implementation, world warp module calculates a differencebetween the location of the target virtual object and the location ofthe target physical object. The difference may be represented as avector, as a degree of rotation, or as a combination of a degree ofrotation and a vector, which, when applied to the virtual environmentwith respect to the physical environment, would result in the targetvirtual object being aligned with the target physical object.

At block 804, a desired world warp is determined based on the locationdifference. For example, if the location difference is represented as adegree of rotation, a desired world warp is determined to be equal tothe location difference. In other words, the desired world warp is aworld warp that, if applied to the virtual environment with respect tothe physical environment, would result in the target virtual objectbeing aligned with the physical object.

However, as is well known in the art, applying an excessive world warpmay be visibly detectable by the user and/or may cause feelings ofmotion sickness for the user. Previous research has shown that as a usermoves his head, translations and/or rotations may be applied to thevirtual environment, which are imperceptible or minimally imperceptibleto the user. For example, if a user rotates his head 90 degrees to theright, rotating the virtual environment 10 degrees left or right may beimperceptible to the user. Accordingly, threshold factors based onchanges in a user's head position (e.g., translation and/or rotation)can be applied to determine a maximum world warp that is likely to beimperceptible to the user. The threshold factors may differ fortranslation as compared to rotation. Furthermore, the threshold factorsmay not be symmetric. That is, when a user rotates his head to theright, the threshold for applying a right rotational world warp may begreater than a threshold for applying a left rotational world warp.Similarly, thresholds for applying vertical translations or rotationsmay differ from thresholds for applying horizontal translations orrotations.

At block 806, a first position of a user's head is determined. Forexample, based on data received from camera 114 and/or sensors 120, aposition of the user's head at a first instant in time is determined.

At block 808, at a later time, a second position of a user's head isdetermined. For example, based on data received from camera 114 and/orsensors 120, a position of the user's head at a second, later instant intime is determined. In an example, the difference between the firstinstant in time and second instant in time is a fraction of a second.

At block 810, a position difference between the first and secondpositions of the user's head is calculated. For example, world warpmodule 608 compares the first position of the user's head with thesecond position of the user's head. The position difference mayrepresent any one or more of a horizontal translation, a verticaltranslation, a horizontal rotation, or a vertical rotation. In anexample implementation, the calculated position difference is a singlevalue that represents a three-dimensional position difference. Inanother example, the calculated position difference may have multiplecomponents representing, for example, a horizontal translation, avertical translation, a horizontal rotation, or a vertical rotation.

At block 812, a maximum world warp is determined based on the calculatedposition difference. For example, world warp module 608 applies athreshold warp factor to the calculated position difference to determinethe maximum world warp. In an example implementation, the maximum worldwarp may be represented as a single value that represents a positionchange in three-dimensional space. In another example implementation,the maximum world warp may be a combination of multiple values. Forexample, a first maximum warp value may be based on a horizontaltranslation of the user's head, a second maximum warp value may be basedon a horizontal rotation of the user's head, and a third maximum warpvalue may be based on a vertical rotation of the user's head.

At block 814, it is determined whether or not the desired world warp isless than or equal to the maximum world warp. For example, as describedabove, the maximum world warp represents a degree to which the virtualenvironment can be warped while likely being imperceptible to the user.At block 814, it is determined whether or not applying a world warpsufficient to align the target virtual object with the target physicalobject is within the threshold maximum world warp.

If the desired world warp is less than or equal to the maximum worldwarp (the “Yes” branch from block 814), then at block 816, the desiredworld warp is applied. For example, world warp module 608 rotates and/ortranslates the virtual environment with respect to the physicalenvironment based on the previously calculated desired world warp,resulting in alignment of the target virtual object and the targetphysical object.

On the other hand, if the desired world warp is greater than the maximumworld warp (the “No” branch from block 814), then at block 818, themaximum world warp is applied. For example, if it is determined that theworld warp necessary to align the target virtual object with the targetphysical object would likely be perceptible to the user, then thenmaximum world warp (that is likely to be imperceptible to the user) isapplied. For example, world warp module 608 rotates and/or translatesthe virtual environment with respect to the physical environment basedon the previously calculated maximum world warp. As a result, a locationdifference between the target virtual object and the target physicalobject will be less than before the world warp, but the target virtualobject and the target physical object will still not be aligned.

FIG. 9 illustrates an example method 900 for calculating a maximum worldwarp based on horizontal and vertical head rotation. At block 902,horizontal and vertical components of the location difference aredetermined. For example, if both the virtual object and the physicalobject are resting on a same surface, the horizontal component of thelocation difference represents the distance between the virtual objectand physical object along the plane of the table surface. If the virtualobject is, for example, stacked on another virtual object, and thevertical component of the location difference represents the verticaldistance between the virtual object and the physical object. If both thevirtual object and the physical object are resting on a same surface,the vertical component of the location difference is zero.

At block 904, a first head position is determined. For example, a firsthead position is represented by face 906. Block 904 may correspond toblock 806 in FIG. 8.

At block 908, a second head position is determined. For example, asecond head position is represented by face 910. Block 908 maycorrespond to block 808 in FIG. 8.

At block 912, a horizontal rotation difference between the first andsecond head positions is determined. For example, the difference betweenface 906 and face 914 represents the horizontal rotation difference,which is attributed to left/right head rotation.

At block 916, a vertical rotation difference between the first andsecond head positions is determined. For example, the difference betweenface 906 and face 918 represents the vertical rotation difference, whichis attributed to up/down head nodding.

Blocks 912 and 916 may correspond to block 810 in FIG. 8.

At block 920, a maximum horizontal world warp is calculated. Forexample, world warp module 608 determines a degree of horizontalrotation represented by the difference between the first and second headpositions. A maximum world warp scaling factor is then applied to thedegree of horizontal rotation to calculate the maximum horizontal worldwarp. As described above, based on a horizontal head rotation, twovalues may be calculated for the maximum world warp (i.e., one for aright rotational warp and one for a left rotational warp). For example,if the user's head rotated toward the right, a first maximum horizontalworld warp may be calculated that would allow for the virtualenvironment to be rotated 49% further to the right and a second maximumhorizontal world warp may be calculated that would allow for the virtualenvironment to be rotated 20% less (effectively rotating the virtualenvironment to the left).

At block 922, a maximum vertical world warp is calculated. For example,world warp module 608 determines a degree of vertical rotationrepresented by the difference between the first and second headpositions. A maximum world warp scaling factor is then applied to thedegree of vertical rotation to calculate the maximum vertical worldwarp. As described above, based on a vertical head rotation, two valuesmay be calculated for the maximum world warp (i.e., one for an upwardrotational warp and one for a downward rotational warp).

Blocks 920 and 922 may correspond to block 812 in FIG. 8.

FIG. 10 illustrates an example method 1000 for dynamically applying abody warp as a user reaches for a virtual object. At block 10002, aphysical location of the user's hand is determined. For example, virtualreality system 126 may track a physical location of the user's handbased on hand tracking device 116 and/or data from camera 114.

At block 1004, a virtual location of the virtual representation of theuser's hand is determined. For example, virtual reality system 126maintains data representing the current location of the virtualrepresentation of the user's hand.

At block 1006, a physical location of the physical object is determined.For example, physical target selection module 604 selects and identifiesthe target physical object 106 to which the virtual object 108 the useris reaching for is mapped. The physical location of the physical objectmay be tracked, for example, by virtual reality system 126

At block 1008, a virtual location of the virtual object is determined.For example, virtual reality system 126 maintains location datacorresponding to the virtual location of the virtual object 108 that theuser is reaching for.

At block 1010, a body warp is determined by calculating a locationdifference between the physical location of the physical object and thevirtual location of the virtual object. For example, body warp module610 calculates a difference between the physical location of thephysical object 106 and the virtual location of the virtual object 108.

At block 1012, the body warp is applied to the virtual representation ofthe user's hand. For example, body warp module 610 translates thevirtual representation of the user's hand within the virtualenvironment, such that a vector describing a path between the physicallocation of the user's physical hand and the physical location of thephysical object has the same distance and direction as a vectordescribing a path between the translated virtual location of the virtualrepresentation of the user's hand and the virtual location of thevirtual object.

FIG. 11 illustrates an example incremental body warp. According to thetechnique described with reference to FIG. 10, a body warp is appliedinitially, when the user first begins to reach for a virtual object. Incontrast, FIG. 11 illustrates a scenario in which the body warp isapplied incrementally such that as the user's hand gets closer to thetarget of the reach, a greater body warp is applied.

For example, as illustrated in FIG. 11, P_(O) represents an initialposition 1102 of the user's physical hand when the user starts to reachfor the virtual object 1104. V_(T) represents the virtual location ofthe virtual object 1104. P_(T) represents the physical location of aphysical object 1106, which is mapped to the virtual object 1104. Vector1108, between the physical location of the physical object 1106 and thevirtual location of the virtual object 1104, represents the total bodywarp to be applied to ensure that when the virtual representation of theuser's hand reaches the virtual object, the user's physical hand reachesthe physical object.

P_(H) represents a current location 1110 of the user's physical hand andV_(H) represents a corresponding current location 1112 of the virtualrepresentation of the user's hand as the user is reaching for thevirtual object 1104. Vector 1114, between the current location of theuser's hand the current location of the virtual representation of theuser's hand, represents an incremental warp to be applied at the currenttime, based on the current locations 1110 and 1112.

FIG. 12 illustrates an example method 1200 for dynamically applying anincremental body warp as a user reaches for a virtual object. The methodillustrated in FIG. 12 may correspond to block 720 of FIG. 7.

At block 1202, an initial physical location of the user's hand isdetermined. For example, as illustrated in, and described above withreference to FIG. 11, the initial hand position may be indicated asP_(O) 1102 as the user begins reaching for the virtual object. Asillustrated in, and described above with reference to, FIG. 7, steps712-720 are repeated as a user reaches for a virtual object. In anexample implementation, P_(O) is determined to be the location of theuser's physical hand the first time step 720 is performed for aparticular target virtual object. The initial physical location of theuser's hand may be tracked by, for example, virtual reality system 126,and maintained by body warp module 610.

At block 1204, a virtual location of the target virtual object isdetermined. For example, virtual reality system 126 may maintainlocation information associated with the virtual object. As illustratedin FIG. 11, the virtual location of the target virtual object may berepresented as V_(T) 1104.

At block 1206, a physical location of the target physical object isdetermined. For example, physical target selection module 604 selectsand identifies the target physical object 1106 to which the targetvirtual object 1104 the user is reaching for is mapped. The body warpmodule 610 determines the location, P_(T), based, for example, onlocation data maintained by virtual reality system 126.

At block 1208, a total body warp is determined. For example, body warpmodule 610 calculates a difference between the virtual location, V_(T),of the target virtual object 1104 and the physical location, P_(T), ofthe target physical object 1106.

At block 1210, a current physical location of the user's hand isdetermined. For example, as described above with reference to block1202, an incremental body warp may be applied multiple times as a userreaches for a virtual object. Accordingly, the first time the body warpis applied, the current physical location of the user's hand, P_(H), isequal to the initial physical location of the user's hand, P_(O).However, as the user moves their hand, P_(O) remains constant, whileP_(H) changes to reflect the current position of the user's hand 1110.

At block 1212, a first vector is determined between the current physicallocation of the user's hand and the initial physical location of theuser's hand. For example, referring to FIG. 11, body warp module 610determines a direction and distance between P_(H) and P_(O).

At block 1214, a second vector is determined between the physicallocation of the target physical object and the initial physical locationof the user's hand. For example, referring to FIG. 11, body warp module610 determines a direction and distance between P_(T) and P_(O).

At block 1216, a warping ratio is calculated based on a differencebetween the first vector and the second vector. For example, body warpmodule 610 calculates a warping ratio, α, such that:

$\alpha = {\max \left( {0,{\min \left( {1,\frac{\left( {P_{T} - P_{O}} \right) \cdot \left( {P_{H} - P_{O}} \right)}{\left( {P_{T} - P_{O}} \right)^{2}}} \right)}} \right)}$

At block 1218, an incremental body warp is determined based on the totalbody warp (see block 1208) and the warping ratio. For example, body warpmodule 610 may multiply the total body warp by the warping ratio tocalculate the incremental body warp.

At block 1220, the incremental body warp is applied to the virtualrepresentation of the user's hand. For example, the virtual position ofthe virtual representation of the user's hand 1112, is translated by theincremental body warp value.

FIG. 13 illustrates an example method 1300 for applying a body-friendlybody warp. As described above with reference to FIG. 4, translating thevirtual representation of the user's hand can result in a virtualrepresentation of a hand that appears to be disconnect from the body orotherwise misaligned with the body. Method 1300 utilizes a rotationaladjustment to maintain a more realistic alignment with between thevirtual representation of the user's hand and the user's body.

At block 1302, an initial virtual hand location is determined. Forexample, body warp module 610 determines a location of the virtualrepresentation of the user's hand when the user began reaching for thetarget virtual object. In an example implementation, this value mayremain constant as multiple body warps are applied over time.

At block 1304, a current virtual hand location is determined. Forexample, body warp module 610 determines a current location of thevirtual representation of the user's hand. In an example implementation,as the user reaches for a target virtual object, the location of thevirtual representation of the user's hand changes.

At block 1306, a virtual location difference is calculated as adifference between the initial virtual hand location and the currentvirtual hand location. For example, body warp module 610 determines avector that represents a direction and a distance between the initialvirtual hand location and the current virtual hand location.

At block 1308, it is determined whether or not the virtual locationdifference is greater than a threshold value. For example, a tolerableamount of misalignment between the user's body and the virtualrepresentation of the user's hand may be represented by the thresholdvalue. In an example implementation, the threshold value may include adirection component and a distance component. For example, a greaterdistance threshold may be tolerable in conjunction with a smaller angledifference.

If the virtual location difference is greater than the threshold (the“Yes” branch from block 1308), then at block 1310, a rotation is appliedto the virtual representation of the user's hand. For example, body warpmodule 610 may rotate the virtual representation of the user's handabout a point coinciding with the user's wrist, to better align theportion of the virtual representation of the user's hand that is closestto the user's body.

On the other hand, if the virtual location difference is not greaterthan the threshold (the “No” branch from block 1308), then at block1312, the process ends.

EXAMPLE CLAUSES

A. A method comprising: mapping a virtual environment to a physicalenvironment to establish an alignment between the virtual environmentand the physical environment; determining, within the physicalenvironment, a physical location of a physical object; determining,within the virtual environment, a virtual location of a virtual object;determining that a user is reaching toward the virtual object; renderingwithin the virtual environment, a virtual hand that represents at leasta portion of the user's hand while the user is reaching toward thevirtual object; and based at least in part on a difference between thephysical location and the virtual location: dynamically adjusting thealignment between the virtual environment and the physical environmentto reduce the difference between the physical location and the virtuallocation; and dynamically adjusting the virtual representation of theuser's hand to cause the user to physically reach for the physicalobject while it appears that the virtual representation of the user'shand is reaching for the virtual object.

B. A method as Paragraph A recites, further comprising: determining afirst position of the user's head while the user is reaching toward thevirtual object; determining a second position of the user's head whilethe user is reaching toward the virtual object; calculating a differencebetween the first position of the user's head and the second position ofthe user's head, wherein the difference indicates a vertical rotation;and dynamically adjusting the alignment between the virtual environmentand the physical environment to reduce a vertical distance between thephysical location and the virtual location.

C. A method as Paragraph A or Paragraph B recites, further comprising:determining a location of the user's physical hand and a correspondinglocation of the virtual hand while the user is reaching toward thevirtual object; determining a virtual vector that represents a distanceand direction between the location of the virtual hand and the virtuallocation of the virtual object; determining a physical vector thatrepresents a distance and direction between the location of the user'sphysical hand and the physical location of the physical object; andbased at least in part on a difference between the virtual vector andthe physical vector, dynamically applying a body warping to adjust thelocation of the virtual hand within the virtual environment.

D. A method as Paragraph C recites, wherein applying the body warpingcomprises: calculating a warping ratio based on the physical location ofthe physical object, an initial location of the user's physical hand,and a current location of the user's physical hand; and adjusting thelocation of the virtual hand within the virtual environment based, atleast in part, on the warping ratio.

E. A method as Paragraph C or Paragraph D recites, wherein applying thebody warping comprises: applying a translation to the virtual hand toadjust the location of the virtual hand within the virtual environment;and applying a rotation to the virtual hand.

F. A method as any of Paragraphs A-E recite, further comprising:repeatedly applying a world warping as the user reaches toward thevirtual object.

G. A method as any of Paragraphs A-F recite, further comprising:repeatedly applying a body warping as the user reaches toward thevirtual object such that a position of the virtual hand intersects withthe virtual location at substantially the same time that a position ofthe user's physical hand intersects with the physical location.

H. A method comprising: mapping a virtual environment to a physicalenvironment to establish an alignment between the virtual environmentand the physical environment; determining, within the physicalenvironment, a physical location of a physical object and a physicallocation of a user's physical hand; determining, within the virtualenvironment, a virtual location of a virtual object and a virtuallocation of a virtual representation of the user's hand; determiningthat a user is reaching toward the virtual object; determining that thevirtual object and the physical object are not aligned, so that, basedon a current trajectory, when the virtual representation of the user'shand reaches the virtual object, the user's physical hand will not reachthe physical object; and dynamically adjusting the virtual location ofthe virtual representation of the user's hand to reduce a differencebetween a vector between the physical location of the physical objectand the physical location of the user's physical hand and a vectorbetween the virtual location of the virtual object and the virtuallocation of the virtual representation of the user's hand.

I. A method as Paragraph H recites, further comprising: repeatedlyadjusting the virtual location of the virtual representation of theuser's hand as the user reaches toward the virtual object such that thevirtual location of the virtual representation of the user's handintersects with the virtual location of the virtual object atsubstantially the same time that the physical location the user's handintersects with the physical location of the physical object.

J. A method as Paragraph H or Paragraph I recites, wherein dynamicallyadjusting the virtual location of the virtual representation of theuser's hand comprises:

applying a translation to the virtual representation of the user's handto adjust the virtual location of the virtual representation of theuser's hand within the virtual environment; and

applying a rotation to the virtual representation of the user's hand.

K. A method as any of Paragraphs H-J recite, wherein dynamicallyadjusting the virtual location of the virtual representation of theuser's hand comprises:

calculating a warping ratio based on the physical location of thephysical object, an initial physical location of the user's hand, and acurrent physical location of the user's hand; and

adjusting the virtual location of the virtual hand within the virtualenvironment based, at least in part, on the warping ratio.

L. A method as Paragraph K recites, further comprising: repeatedlycalculating a warping ratio and adjusting the virtual location of thevirtual representation of the user's hand based, at least in part, onthe warping ratio as the user reaches toward the virtual object suchthat the virtual location of the virtual representation of the user'shand intersects with the virtual location of the virtual object atsubstantially the same time that the physical location the user's handintersects with the physical location of the physical object.

M. One or more computer readable media having computer-executableinstructions stored thereon, which, when executed by a computing device,cause the computing device to perform operations comprising: mapping avirtual environment to a physical environment to establish an alignmentbetween the virtual environment and the physical environment;determining, within the physical environment, a physical location of aphysical object; determining, within the virtual environment, a virtuallocation of a virtual object; determining that a user is reaching towardthe virtual object; dynamically adjusting the alignment between thevirtual environment and the physical environment to reduce a differencebetween the physical location of the physical object and the virtuallocation of the virtual object; and dynamically adjusting a virtuallocation of a virtual representation of the user's hand to increase alikelihood that a physical hand of the user will reach the physicallocation of the physical object at substantially the same time that avirtual representation of the user's hand will reach the virtuallocation of the virtual object.

N. One or more computer readable media as Paragraph M recites, whereindynamically adjusting a virtual location of a virtual representation ofthe user's hand to increase a likelihood that a physical hand of theuser will reach the physical location of the physical object atsubstantially the same time that a virtual representation of the user'shand will reach the virtual location of the virtual object includes:dynamically adjusting a virtual location of a virtual representation ofthe user's hand to reduce a difference between a vector between thephysical location of the physical object and a physical location of theuser's physical hand and a vector between the virtual location of thevirtual object and a virtual location of the virtual representation ofthe user's hand.

O. One or more computer readable media as Paragraph M or Paragraph Nrecites, wherein dynamically adjusting a virtual location of a virtualrepresentation of the user's hand comprises: translating the virtualrepresentation of the user's hand within the virtual environment; androtating the virtual representation of the user's hand within thevirtual environment.

P. One or more computer-readable media as any of Paragraphs M-O recite,wherein dynamically adjusting the alignment between the virtualenvironment and the physical environment to reduce a difference betweenthe physical location of the physical object and the virtual location ofthe virtual object comprises: determining a change in a position of theuser's head; and dynamically adjusting the alignment between the virtualenvironment and the physical environment based, at least in part, on thedetermined change in the position of the user's head.

Q. One or more computer-readable media as Paragraph P recites, whereindynamically adjusting the alignment between the virtual environment andthe physical environment to reduce a difference between the physicallocation of the physical object and the virtual location of the virtualobject further comprises: calculating distance between the physicallocation of the physical object and the virtual location of the virtualobject; and dynamically adjusting the alignment between the virtualenvironment and the physical environment further based, at least inpart, on the distance between the physical location of the physicalobject and the virtual location of the virtual object.

R. One or more computer-readable media as any of Paragraphs M-Q recite,wherein dynamically adjusting the alignment between the virtualenvironment and the physical environment to reduce a difference betweenthe physical location of the physical object and the virtual location ofthe virtual object comprises: determining a change in a position of theuser's head; based, at least in part, on the change in the position ofthe user's head, calculating a maximum adjustment value; and adjustingthe alignment between the virtual environment and the physicalenvironment based, at least in part, on the maximum adjustment value.

S. One or more computer-readable media as Paragraph R recites, whereindynamically adjusting the alignment between the virtual environment andthe physical environment to reduce a difference between the physicallocation of the physical object and the virtual location of the virtualobject further comprises: calculating a distance between the physicallocation of the physical object and the virtual location of the virtualobject; and dynamically adjusting the alignment between the virtualenvironment and the physical environment further based, at least inpart, on the distance between the physical location of the physicalobject and the virtual location of the virtual object.

T. One or more computer-readable media as any of Paragraphs M-Q recite,wherein dynamically adjusting the alignment between the virtualenvironment and the physical environment to reduce a difference betweenthe physical location of the physical object and the virtual location ofthe virtual object comprises: calculating a vertical distance betweenthe physical location of the physical object and the virtual location ofthe virtual object; determining a vertical rotation of the user's head;based on the vertical rotation of the user's head, calculating a maximumadjustment value; and dynamically adjusting a vertical alignment betweenthe virtual environment and the physical environment based, at least inpart on the maximum adjustment value and the vertical distance betweenthe physical location of the physical object and the virtual location ofthe virtual object.

CONCLUSION

Although the techniques have been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the appended claims are not necessarily limited to the features oracts described. Rather, the features and acts are described as exampleimplementations of such techniques.

The operations of the example processes are illustrated in individualblocks and summarized with reference to those blocks. The processes areillustrated as logical flows of blocks, each block of which canrepresent one or more operations that can be implemented in hardware,software, or a combination thereof. In the context of software, theoperations represent computer-executable instructions stored on one ormore computer-readable media that, when executed by one or moreprocessors, enable the one or more processors to perform the recitedoperations. Generally, computer-executable instructions includeroutines, programs, objects, modules, components, data structures, andthe like that perform particular functions or implement particularabstract data types. The order in which the operations are described isnot intended to be construed as a limitation, and any number of thedescribed operations can be executed in any order, combined in anyorder, subdivided into multiple sub-operations, and/or executed inparallel to implement the described processes. The described processescan be performed by resources associated with one or more device 112and/or server 130 such as one or more internal or external CPUs or GPUs,and/or one or more pieces of hardware logic such as FPGAs, DSPs, orother types of accelerators.

All of the methods and processes described above may be embodied in, andfully automated via, specialized computer hardware. Some or all of themethods may alternatively be embodied in software code modules executedby one or more general purpose computers or processors. The code modulesmay be stored in any type of computer-readable storage medium or othercomputer storage device.

Conditional language such as, among others, “can,” “could,” “might” or“may,” unless specifically stated otherwise, are understood within thecontext to present that certain examples include, while other examplesdo not include, certain features, elements and/or steps. Thus, suchconditional language is not generally intended to imply that certainfeatures, elements and/or steps are in any way required for one or moreexamples or that one or more examples necessarily include logic fordeciding, with or without user input or prompting, whether certainfeatures, elements and/or steps are included or are to be performed inany particular example. Conjunctive language such as the phrase “atleast one of X, Y or Z,” unless specifically stated otherwise, is to beunderstood to present that an item, term, etc. may be either X, Y, or Z,or a combination thereof

Any routine descriptions, elements or blocks in the flow diagramsdescribed herein and/or depicted in the attached figures should beunderstood as potentially representing modules, segments, or portions ofcode that include one or more executable instructions for implementingspecific logical functions or elements in the routine. Alternateimplementations are included within the scope of the examples describedherein in which elements or functions may be deleted, or executed out oforder from that shown or discussed, including substantiallysynchronously or in reverse order, depending on the functionalityinvolved as would be understood by those skilled in the art. It shouldbe emphasized that many variations and modifications may be made to theabove-described examples, the elements of which are to be understood asbeing among other acceptable examples. All such modifications andvariations are intended to be included herein within the scope of thisdisclosure and protected by the following claims.

1. A method comprising: mapping a virtual environment to a physicalenvironment to establish an alignment between the virtual environmentand the physical environment; determining, within the physicalenvironment, a physical location of a physical object; determining,within the virtual environment, a virtual location of a virtual object;determining that a user is reaching toward the virtual object; renderingwithin the virtual environment, a virtual hand that represents at leasta portion of the user's hand while the user is reaching toward thevirtual object; determining a location of the user's physical hand and acorresponding location of the virtual hand while the user is reachingtoward the virtual object; and based at least in part on a differencebetween the physical location of the physical object and the virtuallocation of the virtual object: dynamically adjusting the alignmentbetween the virtual environment and the physical environment to reducethe difference between the physical location and the virtual location;and dynamically adjusting the virtual representation of the user's handto cause the user to physically reach for the physical object while itappears that the virtual representation of the user's hand is reachingfor the virtual object, wherein dynamically adjusting the virtualrepresentation of the user's hand includes dynamically applying a bodywarping to adjust the location of the virtual hand within the virtualenvironment, wherein applying the body warping includes: calculating awarping ratio based on the physical location of the physical object, aninitial location of the user's physical hand, and a current location ofthe user's physical hand; and adjusting the location of the virtual handwithin the virtual environment based, at least in part, on the warpingratio.
 2. A method as recited in claim 1, further comprising:determining a first position of the user's head while the user isreaching toward the virtual object; determining a second position of theuser's head while the user is reaching toward the virtual object;calculating a difference between the first position of the user's headand the second position of the user's head, wherein the differenceindicates a vertical rotation; and dynamically adjusting the alignmentbetween the virtual environment and the physical environment to reduce avertical distance between the physical location and the virtuallocation.
 3. A method as recited in claim 1, wherein applying the bodywarping to adjust the location of the virtual hand within the virtualenvironment further includes: determining a virtual vector thatrepresents a distance and direction between the location of the virtualhand and the virtual location of the virtual object; determining aphysical vector that represents a distance and direction between thelocation of the user's physical hand and the physical location of thephysical object; and dynamically applying the body warping to adjust thelocation of the virtual hand within the virtual environment based atleast in part on a difference between the virtual vector and thephysical vector.
 4. (canceled)
 5. A method as recited in claim 1,wherein applying the body warping further includes: applying atranslation to the virtual hand to adjust the location of the virtualhand within the virtual environment; and applying a rotation to thevirtual hand.
 6. A method as recited in claim 1, further comprising:repeatedly applying a world warping as the user reaches toward thevirtual object.
 7. A method as recited in claim 1, further comprising:repeatedly applying a body warping as the user reaches toward thevirtual object such that a position of the virtual hand intersects withthe virtual location at substantially the same time that a position ofthe user's physical hand intersects with the physical location.
 8. Amethod comprising: mapping a virtual environment to a physicalenvironment to establish an alignment between the virtual environmentand the physical environment; determining, within the physicalenvironment, a physical location of a physical object and a physicallocation of a user's physical hand; determining, within the virtualenvironment, a virtual location of a virtual object and a virtuallocation of a virtual representation of the user's hand; determiningthat a user is reaching toward the virtual object; determining that thevirtual object and the physical object are not aligned, so that, basedon a current trajectory, when the virtual representation of the user'shand reaches the virtual object, the user's physical hand will not reachthe physical object; calculating a warping ratio based on the physicallocation of the physical object, an initial physical location of theuser's hand, and a current physical location of the user's hand; anddynamically adjusting the virtual location of the virtual representationof the user's hand based, at least in part, on the warping ratio, toreduce a difference between a vector between the physical location ofthe physical object and the physical location of the user's physicalhand and a vector between the virtual location of the virtual object andthe virtual location of the virtual representation of the user's hand.9. A method as recited in claim 8, further comprising: repeatedlyadjusting the virtual location of the virtual representation of theuser's hand as the user reaches toward the virtual object such that thevirtual location of the virtual representation of the user's handintersects with the virtual location of the virtual object atsubstantially the same time that the physical location the user's handintersects with the physical location of the physical object.
 10. Amethod as recited in claim 8, wherein dynamically adjusting the virtuallocation of the virtual representation of the user's hand comprises:applying a translation to the virtual representation of the user's handto adjust the virtual location of the virtual representation of theuser's hand within the virtual environment; and applying a rotation tothe virtual representation of the user's hand.
 11. (canceled)
 12. Amethod as recited in claim 8, further comprising: repeatedly calculatinga warping ratio and adjusting the virtual location of the virtualrepresentation of the user's hand based, at least in part, on thewarping ratio as the user reaches toward the virtual object such thatthe virtual location of the virtual representation of the user's handintersects with the virtual location of the virtual object atsubstantially the same time that the physical location the user's handintersects with the physical location of the physical object.
 13. One ormore computer readable media having computer-executable instructionsstored thereon, which, when executed by a computing device, cause thecomputing device to perform operations comprising: mapping a virtualenvironment to a physical environment to establish an alignment betweenthe virtual environment and the physical environment; determining,within the physical environment, a physical location of a physicalobject; determining, within the virtual environment, a virtual locationof a virtual object; determining that a user is reaching toward thevirtual object; calculating a vertical distance between the physicallocation of the physical object and the virtual location of the virtualobject; determining a vertical rotation of the user's head; based on thevertical rotation of the user's head, calculating a maximum adjustmentvalue; and dynamically adjusting the alignment between the virtualenvironment and the physical environment to reduce a difference betweenthe physical location of the physical object and the virtual location ofthe virtual object, wherein adjusting the alignment includes:dynamically adjusting a vertical alignment between the virtualenvironment and the physical environment based, at least in part on themaximum adjustment value and the vertical distance between the physicallocation of the physical object and the virtual location of the virtualobject.
 14. One or more computer readable media as recited in claim 21,wherein dynamically adjusting a virtual location of a virtualrepresentation of the user's hand to increase a likelihood that aphysical hand of the user will reach the physical location of thephysical object at substantially the same time that a virtualrepresentation of the user's hand will reach the virtual location of thevirtual object includes: dynamically adjusting a virtual location of avirtual representation of the user's hand to reduce a difference betweena vector between the physical location of the physical object and aphysical location of the user's physical hand and a vector between thevirtual location of the virtual object and a virtual location of thevirtual representation of the user's hand.
 15. One or more computerreadable media as recited in claim 21, wherein dynamically adjusting avirtual location of a virtual representation of the user's handcomprises: translating the virtual representation of the user's handwithin the virtual environment; and rotating the virtual representationof the user's hand within the virtual environment.
 16. One or morecomputer-readable media as recited in claim 13, wherein dynamicallyadjusting the alignment between the virtual environment and the physicalenvironment to reduce a difference between the physical location of thephysical object and the virtual location of the virtual objectcomprises: determining a change in a position of the user's head; anddynamically adjusting the alignment between the virtual environment andthe physical environment based, at least in part, on the determinedchange in the position of the user's head.
 17. One or morecomputer-readable media as recited in claim 16, wherein dynamicallyadjusting the alignment between the virtual environment and the physicalenvironment to reduce a difference between the physical location of thephysical object and the virtual location of the virtual object furthercomprises: calculating distance between the physical location of thephysical object and the virtual location of the virtual object; anddynamically adjusting the alignment between the virtual environment andthe physical environment further based, at least in part, on thedistance between the physical location of the physical object and thevirtual location of the virtual object.
 18. One or morecomputer-readable media as recited in claim 13, wherein dynamicallyadjusting the alignment between the virtual environment and the physicalenvironment to reduce a difference between the physical location of thephysical object and the virtual location of the virtual objectcomprises: determining a change in a position of the user's head; based,at least in part, on the change in the position of the user's head,calculating a maximum adjustment value; and adjusting the alignmentbetween the virtual environment and the physical environment based, atleast in part, on the maximum adjustment value.
 19. One or morecomputer-readable media as recited in claim 18, wherein dynamicallyadjusting the alignment between the virtual environment and the physicalenvironment to reduce a difference between the physical location of thephysical object and the virtual location of the virtual object furthercomprises: calculating a distance between the physical location of thephysical object and the virtual location of the virtual object; anddynamically adjusting the alignment between the virtual environment andthe physical environment further based, at least in part, on thedistance between the physical location of the physical object and thevirtual location of the virtual object.
 20. (canceled)
 21. One or morecomputer readable media as recited in claim 13, further comprising:dynamically adjusting a virtual location of a virtual representation ofthe user's hand to increase a likelihood that a physical hand of theuser will reach the physical location of the physical object atsubstantially the same time that a virtual representation of the user'shand will reach the virtual location of the virtual object.